The laser Raman
(0-3500 cm–1) and FTIR (200-4000 cm–1) spectra (Nujol,
KBr, liquid and vapour) of 2-chloro-5-nitrobenzonitrile have been recorded. A
zero-order normal coordinate analysis has been made for the molecule using
force constants derived earlier. On the basis of potential energy distributions
and eigen vectors unambiguous vibrational assignments have been made for all
the fundamentals of the molecule. The ideal gas state thermodynamic functions
of the molecule are also computed in the temperature range 200-1500 K by
utilizing the observed fundamental frequencies assuming rigid–rotor harmonic
oscillator approximation.